First Minister Peter Robinson has launched a broadside against Sinn Féin over the PSNI arrest of its party leader Gerry Adams.

The Sinn Fein president spent his fourth night in custody being quizzed over the 1972 murder of Jean McConville.

The DUP leader said Sinn Fein “threats” to reassess their future involvement in policing as “despicable”.

Mr Robinson said the PSNI must not be the subject of “republican bullyboy tactics” and must be “free of political considerations”.

Sinn Féin’s Martin McGuinness said on Friday that his party may reconsider its support for the PSNI.

In a statement on Sunday, Mr Robinson said: “The protest action taken by Sinn Féin is unacceptable in any democratic country operating under the rule of law.”

Mr Robinson described what he called a “publicly conveyed threat to the PSNI” from Sinn Féin that “they will reassess their attitude to policing if Gerry Adams is charged” as “despicable” and “thuggish”.

“The PSNI must not be the subject of republican bullyboy tactics,” the DUP leader said.

“They must be completely free to follow any and all evidence regardless of where it takes them and to decide free of political considerations whether suspects will be charged or not.”

Detectives have until 8 pm on Sunday night to charge or release Mr Adams.

They can also reapply to a crown court judge to have his detention extended again. On Friday a senior Belfast judge granted police an extra 48 hours to quiz him at the serious crime suite in Antrim.

Adam is being quizzed about the murder of Mrs McConville, a mother of 10, who was abducted, murdered and secretly buried in 1972.

Deputy First Minister Martin McGuinness said Mr Adams’s arrest was part of an effort by some police officers to “settle old scores, whatever the political cost”.